1. Field
The present disclosure relates to digital media encoded with data for causing a video display output.
2. Description of Related Art
Various methods are known for protecting digital media from unauthorized copying and use. Recent copy-protection schemes for content such as digitally-recorded movies and music have become quite robust and difficult to circumvent. As digital safeguards become more effective, unauthorized copyists of digital content may exploit what is sometimes referred to as the “analog hole” or “analog reconversion.” The analog hole or analog reconversion refers to the universal susceptibility of content to analog copying. To be useful to end users, digital content must at some point be used to generate an analog signal for audio or video output. That analog signal can be captured and re-converted to digital form. The resulting digital copy of the analog output may be of very good quality, depending on the equipment used for the copying process. It may be difficult to discern any difference between output from the original digital media and output from the analog-to-digital copy. Accordingly, the value of digital copy protection schemes may be diminished via copying by analog reconversion.
Generally, a reconverted copy (that is, a digital copy from analog output) will not be identical on a bit-by-bit basis as compared to the original digital source. Therefore, a reconverted copy may be detected by comparing a portion or all of its bits to the original digital copy. For example, any number of selected bits may be compared, or bits making up a digital watermark. However, this detection method requires access to the original bit pattern used for comparison purposes. Such access may not be conveniently available in all applications, thereby limiting the ability to detect reconverted copies.
It is desirable, therefore, to provide a method and apparatus for detecting and disposing of reconverted analog copies, which overcomes the limitations of the prior art.